This invention relates to a ribbon cartridge for use in a serial printer. Although it is useful with many ribbons, in the broad sense of webs, tapes, strands and fabric materials, it is particularly well adapted for use with carbon multi-strike solvent film ribbons.
Ribbon cartridges for serial printers, such as typewriters and, more particularly, high speed character printers, are well known. Two types are in general use.
One type, such as the one shown in Whippo, U.S. Pat. No. 2,986,260, includes a pair of spools on which the inked ribbon is wound. Drive spindles on the printer mechanism extend into the hubs of the supply and take-up spools, and the take-up spool is driven directly by its spindle. This arrangement permits the printer to include a mechanism for reversing the direction of ribbon movement when the supply spool has been exhausted by applying power to the spindle through the supply spool and making it the take-up spool. The ribbon may be reused until the ink on the ribbon no longer produces print of acceptable quality. Because the ribbon spools are driven, however, the rate of movement of the ribbon changes as the amount of ribbon on the take-up spool increases, and the tension in the ribbon as it passes the print head is difficult to control. The amount of ribbon in the cartridge is therefore quite limited.
In other cartridges, the printer drive mechanism engages a capstan on the take-up side of the cartridge. The term "capstan" is used broadly herein to include any rotary device outside the take-up reel hub for advancing the inked ribbon.
In some cartridges of the capstan type, such as the cartridges shown in Lee et al, U.S. Pat. No. 3,974,906 and in Hess, U.S. Pat. No. 4,053,042, the ribbon is an endless band packed randomly in the cartridge. These cartridges are typically limited to fabric ribbons, however, and also hold a limited amount of ribbon.
Other capstan-type cartridges, such as the one shown in Kern, U.S. Pat. No. 4,011,933, include a take-up spool and a supply spool for the inked ribbon. The take-up spool is driven indirectly by an elastic band extending between the capstan and the hub of the take-up spool outside of the cartridge's casing. Such cartridges allow tight packing of film-type ribbon on the spools and provide good print quality, but they are of the single-pass variety and must be discarded or reloaded with ribbon after all of the ribbon has been transferred from the supply spool to the take-up spool. These cartridges also utilize a complex ribbon path because of the tensioning devices utilized and, in some cases, because the supply spool and the take-up reel are not co-planar.
The one-pass capstan-type cartridges also do not take full advantage of present film ribbon technology. The ink on present carbon multi-strike solvent film ribbons is micro-encapsulated in a sponge-like coating on the film substrate. When struck, the coating release a certain amount of ink along the outlines of the character of the element striking the film. The carrier then returns to its original state and reabsorbs ink from the surrounding area. This technology theoretically allows the ribbon to produce five or more impressions per print position. The drive systems of present capstan-type cartridges advance the ribbon about one fourth of a character each time the ribbon is struck. They can not be made to drive the ribbon more slowly because of mechanical limitations in the system. Moreover, because the carrier recovers slowly (on the order of five to ten minutes), the impression made by four consecutive strokes (at rates on the order of fifty-five strokes per second) is not as good as if the ribbon were allowed a significant recovery time before the same area is struck by the print element.
The one-pass capstan-type cartridges also are limited in the size of the character they can produce and are prone to splitting from the edge because of the tensioning design of the cartridge and the proximity of the print element to the edge. In addition, the up and down movement of the cartridge carriage on carriage returns sometimes causes the edge of the ribbon to hang up on a bent "petal" of the print element. Once nicked by the element, the ribbon tears quickly when tension is applied to it. Any splitting or tearing of the ribbon renders it useless, and the cartridge is discarded.